This invention relates generally to air conditioning systems and, more particularly, to an air conditioning system for the rooftop of a bus.
It is recognized, that because of the wide variety of bus types and application requirements, it has been necessary to provide many different types and variations of air conditioning systems in order to meet these different requirements and vehicle interfaces. As a result, the manufacturing and installation costs, and sustaining engineering resources that are necessary in order to properly maintain and service these units, are relatively high.
The common approach for bus rooftop air conditioners is to provide a base frame of rather substantial structural members. The various components of the system are then mounted on or within the base frame, which is then attached to the bus rooftop. Such a frame adds significantly to the cost of a system.
Also associated with the existing bus air conditioning systems is the problem of a component failure causing a compete loss of the air conditioning capacity. That it, with a single large unit as is now customary, failure of that unit such as, for example, a leaking hose causing loss of refrigerant, an electrical failure leading to inoperation of one of the components such as a fan, or a compressor failure, the entire unit is inoperable and no air conditioning can be provided to the unit. In such a situation, it would preferable if partial capacity could be maintained in order to provide a xe2x80x9climp homexe2x80x9d capability.
Traditionally, the condenser coils and fans have been located near the centerline of the bus rooftop, whereas the evaporator coils and fans are closer to the lateral sides of the rooftop. Further, the evaporator fans are of the draw-through type wherein the evaporator fans are placed downstream of the coils and act to draw the conditioned air from the coils. This provides a uniform velocity distribution at the coil but leads to undesirable high jet flow off the fan and subsequently pushing into the bus ducting system. Also, because of the need to have the fan outboard of the coil, it has been necessary to place the coil more toward the center of the bus than might otherwise be desired. Further, draw through disadvantages include hold up of condensate due to the negative pressure at the drain pan, and hat negative pressure can draw back undesirable gases from the bus lower area, such as exhaust gases.
It is therefore an object of the present invention to provide an improved bus rooftop air conditioning system.
Another object of the present invention is the provision for a bus air conditioning system which is effective at all engine operating speeds of the bus, while at the same time does not require an oversized compressor.
Yet another object of the present invention is the provision for reducing the manufacturing, installation, and maintenance costs of a bus air conditioning system.
Still another object of the present invention is that of providing an air conditioning system that is designed for adaptability of use in various types of installation configurations.
Another object of the present invention is that of providing a xe2x80x9climp homexe2x80x9d capability in the event of certain component failures.
Still another object of the present invention is the provision in an evaporator section of a bus rooftop air conditioning system for locating the evaporator coil more toward the lateral edges of the bus.
Still another object is to avoid the problem of negative pressures at the drain pan
Yet another object of the present invention is the provision for a bus rooftop air conditioning system which is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following descriptions when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, an air conditioning module is assembled with its condenser coil, evaporator coil and respective blowers located within the module and so situated that a standard module can accommodate various installation interfaces with different types and locations of return air and supply air ducts on a bus.
In accordance with another aspect of the invention, rather than a large single air conditioning unit, a plurality of relatively small modules can be installed on the roof of a bus, with each being capable of operating independently of the others so as to allow for the relatively low cost mass production of identical standardized units and also provide for a limp home capability in the event of failure of one or more units.
In accordance with another aspect of the invention, each of a plurality of modules are installed in a centered relationship with respect to a longitudinal centerline of the bus and extend transversely across the width of the bus. A single unit with one condenser section and one evaporator section is provided and a double unit with two evaporator sections and two condenser sections are also provided. The number and combination of such modules installed is dependent on the total air conditioning capacity requirement of the bus, and the evaporator sections can be easily ganged to meet with a single return air opening in the bus.
In accordance with another aspect of the invention, the modules have an integrated framework in that various components are assembled in a unibody arrangement to provide structural support for the system.
By yet another aspect of the invention, each of the modules include all the necessary components with electrical power being provided to the electrical components by an inverter/controller that is powered by an engine driven generator.
By another aspect of the invention, the evaporator blower is placed inboard of the evaporator coils and acts to blow air from the return air duct through the coils to be cooled and provide pressurized condensate system thus avoiding condensate hold up and introduction of external gases.
By still another aspect of the invention the evaporator section of the module has a return air plenum that spans a substantial width of the bus to thereby accommodate various sizes and types of return air interface requirements.
In the drawings as hereinafter described, a preferred embodiment is depicted; however various other modifications and alternate constructions can be made thereto without departing from the true spirit and scope of the invention.